********pricetheory.uchicago.edu/levitt/Papers/LevittUnderstandingWhyCrime2004.pdf
btw, here is a newer study looking at all he factors that have contributed to the drop in crime rate...
My suggestion to the further crime reduction is
1. Re-evalute fitness of many parents and promote adoption of kids whose parents are not capable of raising them (heavy drug-users, unemployed, etc)..........
2. Limit government aid to, say, one year, one kid....so it doesn't encourage having additional kids in a not "suited for kids" environment..........